Just another possibility.  I had a similar problem once. Tried everything
without much success.  Turns out that I had replaced the AFM with a rebuilt
AFM a while ago, van ran fine until the valve on the rebuilt one got stuck
open half way.  After I fixed it, all was well again.

Alfred
85 Westy

----- Original Message -----
From: "BJ Feddish" <bfeddish@NETREACH.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, March 05, 2008 2:40 PM
Subject: Still running like crap, the saga continues

> OK, awhile back I posted about my van hesitating. If you remember I took
> it
> to my mechanic who cranked the AFM screw to get it to run rich. The
> hesitating went away, the van ran pretty good but I was down to 11 MPG.  I
> took it back, he cranked it back the other way, still ran OK but now we
> had
> more hesitation. This type of hesitation was where there was a power loss
> for a few seconds then the engine went back to normal. I thought I could
> deal with this until spring but then it started stalling at lights and my
> mileage was still crap. I decided to take it to a well known shop about 45
> NE of me. They fixed my ground wires, replaced the O2 wire and set my
> timing, idle and C02 to factory specs. After a vacuum check everything
> looked fine except a slight leak at the throttle body.  I thought I was
> going to be getting a great running van back but that was not the case.
> Low
> speed is worse than it's ever been. It's almost as if there was a tennis
> ball under the gas pedal. If I'm trying to accelerate in 2nd gear there
> just
> seems to be no power. There are no "big" hesitations but now I have allot
> of
> little ones like someone was tapping on a switch.  The low power at low
> speeds is frightening.  The van idles fine now and traveling at high
> speeds
> seems to be slightly better than before this latest change.  I'd like to
> call them back and see what else we can do but I'm kind of upset they let
> me
> drive the van out of the shop in that condition.  Anyway, can this small
> vacuum leak in the throttle body be the cause or is there something else I
> should be looking at? Is it time to just start replacing parts?
>
> BTW, I just check the timing and it was dead on the V mark.
>
> Also, nobody has been able to find the "thump-thump-thump" noise emanating
> from the rear. 2 places think it "could" be the axel. I can't wait for the
> tow truck ride to discover what that is....
>
> Thanks,
> Bryan